The present invention relates generally to a fuel tank mounting and protecting cage for use with vehicles such as school buses.
The prior art protective cage and mounting device for vehicle gas tanks has proven successful in protecting the fuel tank against rupture in the event of an accident. FIG. 1 illustrates the prior art protective cage and fuel tank mounting mechanism, that were used on vehicles of the assignee of this patent. The protective cage is constructed from round tubing made of high carbon steel. The fuel tank has not been shown in FIG. 1 to better illustrate the fuel tank mounting mechanism and the protective cage. In this prior art device, the fuel tank is anchored to the longitudinal side of a vehicle frame rails, through the mounting mechanism. The fuel tank mounting mechanism includes a plurality of hanger brackets that are secured along their vertical legs to the vehicle frame rails. The fuel tank is supported on a shelf formed by the horizontal legs of the hanger brackets. Hold down devices secure the fuel tank to the hanger brackets. A heat shield is shown secured to the bottoms of the fuel tank hanger brackets.
The protective cage is also secured to the vehicle frame rail, and surrounds the three exposed sides of the fuel tank. The closed ends of the fuel tank add rigidity to the end sections of the fuel tank; however, the midsection of a fuel tank may be less rigid and therefore may be more vulnerable. An elongated angle member is connected to the protective cage and to the hanger brackets. However, this angle member is connected to the round tubing of the protective cage through hanger brackets which may not function to unite the protective cage and the fuel tank mounting mechanism such that they function as a unit in the event of a crash.
It has been asserted that, under some situations, a fuel tank that is mounted and protected by the above prior art mechanism could be ruptured. Although the prior art protective cage does provide protection for the mid-section of the fuel tank, because of the possible vulnerability of this section of the fuel tank compared to the end sections and the possibility that the protective cage could be bent into engagement with the fuel tank mid-section, additional protection will be provided for this area of the fuel tank. It is felt that the midsection of a fuel tank may be vulnerable, especially in the event of a side collision that is concentrated around the mid-portion of the protective cage. In such a collision, the prior art protective cage could collapse in on the fuel tank rather than transfer the impact force through the protective cage to the vehicle frame rails.
Within the space constraints imposed by the wall of the fuel tank and the inside surface of the side skirting of the vehicle, a circular cross-section is not the most efficient cross-section. Instead, a beam of rectangular cross-section can be better used to resist an externally imposed force. Also the high carbon steel from which the prior art protective cage was fabricated can be distorted by a relatively smaller force and thus absorbs a correspondingly smaller amount of impact force.